This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-105153, filed Apr. 6, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an electronic shelf label system (ESL system) for radio-controlling a plurality of electronic shelf labels which are disposed on shelves or products such as goods and which display information on products such as the names of products and the prices of products.
FIG. 9 shows a conventional electronic shelf label system for radio-controlling a plurality of electronic shelf labels.
According to this ESL system, a k-number of shelves 1-1, 1-2, . . . , 1-k are arranged on a sales floor, and an n-number of electronic shelf labels (ESLs) 2-1, 2-2, 2-3, . . . , 2-n are disposed on the k-number of shelves 1-1, 1-2, . . . , 1-k. 
In addition, according to this ESL system, an electronic shelf label server (ESL server) 3 for managing the ESLs 2-1 to 2-n is installed in an office, etc., and a radio communication base station 5 is connected to the ESL server 3 via a wired network 4. The radio communication base station 5 is disposed, for example, on the ceiling of the sales space.
The radio communication base station 5 has a function of performing bidirectional radio communication between itself and the ESLs 2-1 to 2-n of the shelves 1-1 to 1-k in a xe2x80x9c1-to-nxe2x80x9d relationship in the range of about 30 m in radius. Each of the ESLs 2-1 to 2-n has a liquid crystal display (LCD) for displaying a products price.
The ESL server 3 manages products information. The products information is associated with ID information of the ESLs which display the products information. The products information is radio-transmitted to each ESL, 2-1 to 2-n, via the radio communication base station 5.
Each ESL, 2-1 to 2-n, detects the ID information contained in the received information, selects information directed to its own address, and displays products information on the LCD.
Each ESL, 2-1 to 2-n, radio-transmits an affirmative response to the radio communication base station 5 if the reception result is correct, and a negative response to the base station 5 if the reception result is incorrect. On the other hand, each ESL, 2-1 to 2-n, radio-transmits no response to the radio communication base station 5 if the ESL is unable to confirm, owing to bad condition of reception, that the received information is directed to its own address.
In the ESL system, the radio communication base station 5 is required to exactly perform bidirectional communication between itself and the ESLs 2-1 to 2-n within a range of about 30 m in radius. If a frequency band of, e.g. 2.4 GHz is used by the radio communication base station 5 and the ESLs 2-1 to 2-n, a transmission power of about 10 mW is necessary.
However, in order that the ESL may output a transmission power of 10 mW which is out of the range of weak radio wave standards, it is required to obtain legal recognition for wireless LAN apparatuses. In order to acquire such recognition, there is a problem in that some strict technical conditions need to be satisfied, for example, conditions for frequency deviation, occupancy frequency bandwidth and spurious emission level.
Consequently, the ESL needs to use, as a radio communication circuit, a proper circuit including a quartz oscillator with high frequency stability and a radio frequency filter with high selectivity, resulting in an increase in cost.
Moreover, the ESL that produces an output of 10 mW has a large power consumption. If it is driven by a cell, power consumption is great and the cell needs to be changed at short cycles.
Jpn. Pat. Appln. KOKAI Publication No. 63-87837, for instance, discloses a radio data communication system aiming at solving the above problems. This communication system, as shown in FIG. 10, has a private branch radio station A-1. The radio station A-1 transmits/receives data which is transmittable/receivable in a predetermined area R including a plurality of service areas R1, R2, R3, . . . .
The private branch radio station A-1 is connected by means of a transmission path to one of the service areas, for example, a weak-radio-wave radio relay station A-2 having the service area R1. Thus, the radio station A-1 and relay station A-2 constitute a stationary radio station network.
Using relatively strong transmission radio waves, the private branch radio station A-1 transmits data to a plurality of data communication mobile radio terminals A-3 to A-n, which use weak radio waves and are present within the area R including the service areas R1, R2, R3.
When data is to be transmitted from each data communication mobile radio terminal, A-3 to A-n, to the private-branch radio station A-1, the data communication mobile radio terminal, A-3 to A-n, first sends the data to the radio relay station A-2 in the service area using weak radio waves. The radio relay station A-2 then sends the received data to the private branch radio station A-1 using relatively strong transmission radio waves.
When this radio data communication system is applied to the ESL system, the data communication mobile radio terminals correspond to the electronic shelf labels (ESLs). Accordingly, it is assumed that the ESL transmits data to the radio relay station A-2.
In one method of installing the radio relay station A-2, the radio relay station A-2 may be disposed on the ceiling just above the shelf. However, if the height of the ceiling is great, the distance between the ESL and the radio relay station A-2 increases. In such a case, if the ESL uses weak radio waves, the service area that the radio relay station can manage is narrowed.
In order to solve this problem, the radio relay station may be directly disposed on the shelf. Most of shelves are not equipped with power supply wiring, since they are frequently moved. Thus, if the radio relay station is directly disposed on the shelf, the radio relay station would be battery-powered.
In some cases, about 600 kinds of products are densely arranged in one shelf. In such cases, as many (about 600) ESLs are to be disposed on the shelf.
Accordingly, one radio relay station performs radio communication, while managing about 600 ESLs.
Under the circumstances, the radio relay station has to radio-relay a great number of electronic texts. If the radio relay station is battery-powered, the power consumption of the battery is high, and frequent replacement of the battery is necessitated.
The object of the present invention is to decrease a transmission/reception operation time period in a radio relay station, and, when the radio relay station and electronic shelf labels (ESLs) are powered by cells, to reduce the power consumption in the ESLs and increase the lifetime of cells, and also to reduce the power consumption in the radio relay station and increase the lifetime of the cell.
To achieve the object, the present invention provides an electronic shelf label (ESL) system comprising: a plurality of electronic shelf labels (ESLs), disposed on either of a shelf and products, for displaying information including products information; an electronic shelf label (ESL) server for managing the ESLs and transmitting information including the products information with ID information to the ESLs; a radio communication base station for radio-transmitting the information from the ESL server to the ESLs; and a radio relay station for receiving response information from each of the ESLs and transmitting information based on the response information to the radio communication base station.
Each of the ESLs radio-transmits the response information with ID information by means of weak radio waves, upon receiving the information from the radio communication base station.
The radio relay station is located closer to the ESLs than to the radio communication base station. The radio relay station receives the response information on the weak radio waves from each of the ESLs and also receives the information transmitted from the radio communication base station to the ESLs. The radio relay station detects, on the basis of the ID information, the ESL which failed to normally receive the information, and radio-transmits to the radio communication base station information indicative of this ESL.
The radio communication base station, upon receiving the information indicative of the ESL which failed to normally receive the information, transmits this information to the ESL server. The ESL server, upon receiving the information indicative of the ESL which failed to normally receive the information, re-transmits the information to this ESL via the radio communication base station.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.